Because interfaces of the conventional personal computers, used to connect to external peripheral devices, are incapable of supplying high power or cannot supply power to external devices at all, most externally connected devices must utilize commercial power and thus fail to provide portability and accessibility. Because scanners are equipped with a plurality of components of high power consumption and lacks excellent power management, no solution has been found to reduce its high power consumption. Conventional scanners, thus, also fail to provide portability and accessibility. This invention discloses a battery-powered scanner that can be operated in any environment. The battery-powered scanner uses components of low power consumption and reliable power management so as to attain the effect of both accessibility and environmental protection. This invention further remedies the problem of insufficient power supplied by the interface.